Samsung S22 cannot find Sonos system, but Samsung tablet and Google Assistant can

Hi all

I have a multiroom system consisting of;

Family Room: Arc connected via ethernet to network and via HDMI to Samsung TV. Also 2 x Symfonisk connected via WiFi acting as rears

Kitchen: 2 x Symfonisk connected via WiFi acting as stereo pair

Living Room: 2 x Symfonisk connected via WiFi acting as stereo pair

All of these speakers are linked to Google Assistant accessible via Nest Hubs & speakers. I do not have Google Assistant enabled on the Sonos Arc.

The Family Room is exclusively used as surround sound for the Samsung TV

I usually control the other rooms via Google voice control (eg, "Hey Google play my rock playing on Kitchen"). This works fine and I can easily skip tracks, pause, stop and control volume via voice commands. If I wish to search for something specific I can bring up the Sonos app on my phone (Samsung S22 Ultra) or tablet (Samsung Tab S5E), whichever is closest to hand.

For the past few months, my S22 is unable to find my Sonos system, and it appears greyed out in the app and 8 just get the message "Unable to find your Sonos system". Of course, I'm invited to fix this by running through the setup again.

* No, I did not change my router or network settings, or unplug an ethernet cable from a Sonos product

* My products are plugged in and powered on 

* The app knows about all my devices, lists them, but cannot find them

* Yes, the Sonos Arc is connected via ethernet

After this I'm expected to unplug all my speakers, then power them back on. I'm expected to power off my router, wait 10 minutes, then power it back on. I'm expected to reset all the Sonos devices and reinstall them.

The problem I have is that all the devices are visible via the Sonos app on my tablet, correctly assigned to rooms, and perfectly controllable via the app. All the devices are visible to Google Assistant and perfectly controllable via voice control. 

I'm very reluctant to start tearing down the Sonos setup when it's working perfectly via the app on my tablet and via Google Assistant. 

I've rebooted my phone, I've signed out/in on the app, I've force-stopped the app. I've uninstalled/reinstalled the app. None of this fixes the issue

My network consists of a Unifi gateway with an ethernet-connected AP in each room. The Sonos devices on WiFi usually (but not always) connect via the AP in the relevant room. I don't consider this to be part of the problem because it works fine via the app on the Samsung tablet.

Does anyone have any ideas?